SOVIETS UNTIE SNAG IN ACCORD ON NEWER ARMS

WASHINGTON -- The Soviet Union has told the United States it agrees that the pending treaty on medium- and shorter-range missiles bans futuristic weapons, administration officials said on Sunday.

The Soviet statement, which came in a recent letter from Foreign Minister Eduard Shevardnadze, appears to remove an important political obstacle in the Senate to swift approval of the treaty.

The Senate Armed Services Committee complained in a report last month that the accord was vague about whether it banned possible new types of weapons, such as medium-range cruise missiles that destroy their targets by laser beams or other futuristic means, instead of exploding warheads.

The Democratic majority leader, Sen. Robert Byrd of West Virginia, has called this a key issue and said that he would not permit the treaty to come to the Senate floor until the question was resolved.

The Reagan administration has taken the position that the "commonly understood" language in the treaty indicates that such futuristic weapons are prohibited by the pact and has argued that there is no reason to think that Moscow thinks otherwise.

But administration officials have also acknowledged that the Soviet and American negotiators had not specifically discussed whether such futuristic weapons would be covered. And last week, two former Reagan administration officials -- former Defense Secretary Caspar Weinberger and Kenneth Adelman, the former director of the Arms Control and Disarmament Agency -- sent separate letters to Congress asserting that there was no clear understanding between Washington and Moscow that such futuristic weapons are to banned by the treaty.

In order to ease Senate concerns, Secretary of State George Shultz sought a definitive clarification of the issue when he met with Shevardnadze and senior Soviet arms control officials in Geneva on Thursday.

The Russian officials at first seemed to be surprised by Shultz's request, administration officials said. But Yuri Dubinin, the Soviet ambassador to Washington, delivered a letter to the State Department from Shevardnadze on Friday evening, in an apparent effort to help gain quick Senate approval of the treaty.

Shevardnadze wrote that Moscow agreed with the administration's understanding that weapons that destroy targets by futuristic means are banned.